1. Field of the Invention
The present invention generally relates to the field of
frames and, in particular, the present invention is concerned with frames made from a structural box beam construction.
II. Background of the Invention
The ideal vehicle frame has a high strength to weight ratio, maintains its shape under heavy stress, and provides a convenient means for fastening various parts of the vehicle such as bodybolts, suspension system, exhaust system, engine transmission etc. to the frame. In addition the ideal vehicle frame must be inexpensive to produce. A vehicle frame having hollow box frame siderails meets many of the above requirements. Heretofor, the methods employed for attaching the various parts to the frame in a box frame construction have detracted from the goals of lightweight and low cost. In the past, the users of box frames welded flanges, projections, and reinforcing pads to the siderail to provide the attacment points required for the various vehilce parts. However, welding pads etc. to the box frame adds weight and is costly. The placing of aligned apertures in the siderails through which fasteners such as bolts can be inserted is attractive, but the walls of the box beam must be heavy enough to withstand the bolt tension without collapsing. Inserts of cast iron or steel placed inside the box frame between the sides of the box with the bolt passing through the insert effectivly prevent collapsing of the walls but add weight. In addition, these inserts must be positioned properly before the box is closed and held in position until the bolts are inserted. Spacer tubes that extend between the sides of a box frame are ideal in that they weigh very little and are not expensive and they prevent the collapsing of the sides of a box frame when the bolts or attachment means are tightened. The spacer tubes must be held in position while the box beam is closed and the tubes must be held in alignment with their appropriate aperture in the siderail during the assembly process. In the past, this has been accomplished by tack welding the tube in position over the aperture in the sidewall of the box frame. This is expensive and awkward since the welder must first position the tube over the appropriate aperture and then close his helmet and strike the arc to tack weld the tube in place. The welder is essentially blind until the arc is struck and the tube can move slightly out of position during the welding. Furthermore, the cooling of the weld bead may move the tube out of position or cause the tube to cock and go out of perpendicularity with the sidewall of the frame. This requires a straightening procedure which is time consuming and expensive.